Radiation therapy uses high energy radiation beams to kill cancerous cells. Radiation therapy is commonly prescribed for the treatment of cancer, and about half of all cancer patients receive some type of radiation therapy throughout the course of treatment. Radiation therapy is known to kill healthy cells as well as cancerous cells, and has come under scrutiny for side effects.

Administering Radiation Therapy

Radiation therapy may be delivered to the body using a machine to deliver it externally or radioactive materials may be placed inside the body next to cancer cells. Radioactive materials may also be injected or given orally in order to travel through the body to the site of the cancer. Many factors are used to determine the type of radiation therapy that the cancer patient will receive, especially where in the body the cancer is located and how close the cancer is to tissue or organs that are sensitive to radiation.

Other factors used to determine whether and how radiation therapy will be administered include:

  • Type of cancer
  • Size of tumors and stage
  • Patient’s medical history
  • Patient’s age and condition
  • Other types of cancer treatment that will be administered


External Beam Radiation Therapy

This type of radiation therapy is delivered to the body using a machine. Photon beams, either X-rays or gamma rays, are concentrated on body areas during external beam radiation therapy. Patients go through a number of sessions, which is decided upon by the treating physician.

One commonly used type of radiation therapy, called three dimensional conformal radiation therapy, uses computer software and advanced machines to deliver a dose of radiation therapy to specific areas. There are many other types of radiation therapy that are currently being tested. Some use imaging scans such as CT scans and MRIs to deliver images of the body areas continually as the therapy is being administered so that the physician can see if the therapy is having an effect.

Internal Radiation Therapy

Internal radiation therapy is often called brachytherapy. There are several types of brachytherapy. In Interstitial brachytherapy, a radiation source is placed directly inside of tumor tissue. In intercavitary brachytherapy, a radiation source is placed within a body cavity. In episcleral brachytherapy, a radiation source is placed close to the eye. These units of radiation are placed using needles or catheters into the body. In some instances, the units are removed afterwards, in others the unit will not harm the body and is left inside.

Systemic Radiation Therapy

When undergoing systemic radiation therapy, a patient is either injected or swallows a radioactive substance, and the substance travels through the body to the site of the cancer. There are different types of substances that are used to treat the different cancers. Many drugs are now being tested that deliver radiation to a site inside the body. These drugs can be helpful because the radiation is encased in nonradioactive material, which helps protect other body cells from the radiation as the drug travels through the body.

Side Effects of Radiation Therapy

Side effects of cancer radiation are mostly caused by damage to healthy cells. Side effects may occur during treatments, or months or years after treatments have ended. Side effects that occur during treatment are called acute, and may go away after treatment ends. Side effects that occur after treatment are known as chronic, and are usually permanent unless treated. Side effects may differ depending on what area of the body was being treated.

Acute side effects from cancer radiation include:

  • Fatigue
  • Skin problems
  • Hair loss
  • Damage to salivary glands
  • Urinary problems
  • Nausea


Chronic side effects from cancer radiation include:

  • Memory loss
  • Infertility
  • Second cancer
  • Damage to the bowels
  • Development of excessive scar tissue, sometimes restricting movement

Deciding to Use Radiation Therapy

Factors such as genetics and lifestyles habits may have an influence over whether or not side effects develop. When deciding whether or not to use radiation therapy as a cancer treatment, oncologists, physicians, and patients must weigh the potential risk and benefits. Patients should express any concerns surrounding beginning radiation therapy, as emotional and psychological factors may play a role in magnitude of side effects and effectiveness of treatment.




“Radiation Therapy for Cancer.” National Cancer institute. U.S. Department of Health and Human Services, 30 Jun 2010. Web. 22 Nov 2013. <http://www.cancer.gov/cancertopics/factsheet/Therapy/radiation>.

“Radiation Therapy.” Mayo Clinic. Mayo Foundation for Medical Education and Research, 13 Jul 2013. Web. 22 Nov 2013. <http://www.mayoclinic.com/health/radiation-therapy/MY00299>.

“Side Effects of Radiation therapy.” Cancer.net. American Society of Clinical Oncology, 04 Mar 2013. Web. 22 Nov 2013. <http://www.cancer.net/all-about-cancer/cancernet-feature-articles/treatments-tests-and-procedures/side-effects-radiation-therapy>.